Research On Electronically Steerable Antenna Based On Active Frequency Selective Surface

Recent years, with the development of communication industry, the amount of usersincreased significantly, frequency spectrum resource become more and more critical. Forthe very purpose, a serial new technology emerged. In many of these, smart antennabecome one of the frontier technologies by the means of user capacity and frequencyspectrum using efciency.In a common smart antenna system, a linear or circular array is always employed.Beam-forming ability is achived by cntrolling the relative phases of array elements. Phasecontrolling is usually realized by phase shifters, with a serial relative algorithm. Thus,radiation pattern is controlled. Phase shifters always contribute a lot to the total cost ofthe smart antenna system. For this reason, a lot researchs focused on the non-phase-shiftersmart antenna systems or so called electronically steerable antennas.In this essay, a research on the electronically steerable antenna based on active fre-quency selective surface is studied. The theoretically discussion, simulation and prototypetesting are token out to verificate the theory and design.A novel structure and relative theory is presented. The ability of electronically steer-ing is achived by controlling the status of the specially designed active frequency selectivesurface which surrounding a ominidirectional antenna. Single beam modes which coverthe whole horizontal plane and continuously tunable is achived by diferent configura-tions. Further more, multi-beam mode is also achived.Focusing on this special antenna structure, radiation feature is studied. Near field ofthis antenna is divided into three parts. Re-radiation theory is used to deduce the radiationfrom a common linear arry to circular array, further to a conformal array, and finally toESRRA (Electronically steerable radiators and reflector array) antenna. The array modleis established.Active frequency selective surface (AFSS) is a new method to realize electronical-ly steerable ability. In essay, the special requirements of AFSS for purpose of realizingESRRA antenna are studied and a serial of inequations are established. The basic theoryof AFSSes for ESRRA is established. A critical problem for AFSS is the couple inter-ference between unit cells caused by biasing network. To solve this problem, a novel non-biasing-network AFSS topology is presented. Relative simulation is accomplishedand the correctness of this design is proved. A novel magnetic loop trap structure is p-resented. An AFSS with narrow reflection band; high reflection rate in reflection band;high transmission rate in transparent band and polarization sensitive direction being thesame with the unit cells extend direction is achived. Furthermore, a new biasing networkis established systematically. Inductors are mounted on the gap of the biasing networkto isolation the interference. Both the simulation and tested results show that the AFSSmeets the requirements mentioned before.To prove the correctness of the theory, a compact an another high gain ESRRAantenna are fabricated. The test results perfectly meet the theory.In totally, a novel method to build electronically steerable antenna is established.Measured results show that this antenna is high gain in E-plane, flexible continuouslysteerable in H-plane, low power consumption and low cost.